1. Field of the Invention
This invention relates generally to the field of photovoltaic arrays, and more particularly to performing maximum power point tracking on the photovoltaic arrays using pseudo random bit sequences.
2. Description of the Related Art
Photovoltaic (PV) arrays (more commonly known and referred to as solar arrays) are a linked collection of photovoltaic, or solar panels, which typically consist of multiple interconnected solar cells. The modularity of solar panels facilitates the configuration of solar (panel) arrays to supply current to a wide variety of different loads. The solar cells convert solar energy into direct current electricity via the photovoltaic effect, in which electrons in the solar cells are transferred between different bands (i.e. from the valence to conduction bands) within the material of the solar cell upon exposure to radiation of sufficient energy, resulting in the buildup of a voltage between two electrodes. The power produced by a single solar panel is rarely sufficient to meet the most common power requirements (e.g. in a home or business setting), which is why the panels are linked together to form an array. Most solar arrays use an inverter to convert the DC power produced by the linked panels into alternating current that can be used to power lights, motors, and other loads.
The various designs proposed and developed for solar arrays typically fall into one of two configurations: a low-voltage configuration (when the required nominal voltage is not that high), and a high-voltage configuration (when a high nominal voltage is required). The first configuration features arrays in which the solar panels are parallel-connected. The second configuration features solar panels first connected in series to obtain the desired high DC voltage, with the individual strings of series-connected panels connected in parallel to allow the system to produce more current. Various problems have been associated with both configurations, with the most prolific array configuration being the high-voltage series-string based configuration. The series-string configuration raises the overall distribution DC-bus voltage level to reduce resistive losses. However, in doing so it increases panel mismatch losses by virtue of the series-string being limited by the weakest panel in the string. In addition, the resultant DC-bus voltage has a significant temperature and load variance that makes inversion from DC to AC more difficult. Consequently, many design efforts have been concentrated on improving the efficiency of the collection of electrical power from the array, by mitigating these non-idealities.
Various designs have been proposed and developed for DC/DC (DC-to-DC) converter systems applied to solar arrays. Most of these designs have concentrated on the implementation of Maximum Power Point Tracking (MPPT), which employs a high efficiency DC/DC converter that presents an optimal electrical load to a solar panel or array, and produces a voltage suitable for the powered load. Most DC-DC architectures used for PV optimizers do not feature significant small-signal isolation between power inputs and outputs. A signal introduced on an optimizer's input appears at its output. Likewise, a signal introduced on an optimizer's output appears at its input. As it passes from input to output or output to input, this signal may be attenuated, or in some cases, it may be amplified. This poses a particular problem for optimizers that perform MPPT simultaneously within the same array. A probe signal intentionally injected on any first optimizer's input for the purposes of local MPPT unintentionally appears at its output, with consequences for a second optimizer connected in series or parallel.
Many other problems and disadvantages of the prior art will become apparent to one skilled in the art after comparing such prior art with the present invention as described herein.